想要防止smurf攻击，可以在交换机上配置以下哪个命令策略？
Aanti-attack abnormal enable
Banti-attack smurf enable
Cdefend-policy smurf enable
Ddefend-policy icmp-attack-set enable
Aanti-attack abnormal enable
Banti-attack smurf enable
Cdefend-policy smurf enable
Ddefend-policy icmp-attack-set enable